Cache-A slow writes

[Tom Goldberg]

Hi Jack,

Your slow performance can be due to a few things – possibly tape drive issues but more likely an overly large number of files on this tape or possibly your tape catalog has grown so large it it taking too much time.

LTFS itself gets bogged down in any archive where content is stored as individual frames. If you think this might be the problem, try doing a tar archive on the content instead and see if the performance is better.

If you think it is might in fact be your tape catalog, you can try deleting some older tapes from the catalog if you don’t need to track them anymore or can afford to track them externally (how to export your catalog is in a document linked below). You can also try a database repair by logging in to the unit for a terminal session as described in the other document linked below and execute the following commands:
(Commands must be in order – its a good idea to backup your catalog first)
/etc/init.d/httpd stop
/etc/init.d/tapemgr stop
/etc/init.d/mysqld stop
cd /media/catalog/database/mysql/catalog
myisamchk *.MYI
myisamchk --recover ‘toc’
myisamchk --recover ‘inode’
myisamchk --recover ‘file’
myisamchk *.MYI
/etc/init.d/mysqld start
/etc/init.d/tapemgr start
/etc/init.d/httpd start


If you think it might be the tape drive itself, you can always run a cleaning tape pass which might help. Or if you want to actually check the health of the tape drive, the full suite of HP tape tools are on your system – you can run them from the command line by typing /opt/ltt/hp_ltt Instructions for using these tools can be found in HP’s online documentation but it is menu driven and you may be able to figure it out by poking around.

Instructions for logging into the Cache-A’s command line can be found at
https://tomgoldberg.net/Cache-A/CATechBrief-CommandLine.pdf

The Cache-A tech brief describing how to export your catalog is at:
https://tomgoldberg.net/Cache-A/CATechBrief-catalog-export.pdf

Tom Goldberg
TGCS
30201 Rainbow Hill Rd.
Evergreen, CO 80439
mailto:tomgoldberg@gmail.com
https://tomgoldberg.net

[Jack Mcgee]

Thanks Tom.

I tried writing a small number of files to a newly formatted TAR tape.

It is still very slow to the point of being unusable.

The HP tools Drive Assessment says the drive passed.

I have repaired the Cache-A database. How would I just delete the database and start from scratch to see if that is the problem. And then restore it from backup?

[Tom Goldberg]

Unfortunately there is no way for a user to restore the database from backup (we never did finish developing that capability) – the only folks who can do that at this point in time is ProMax support.

It still sounds like it might just be too much data in the library, but alternately you may possibly be having HDD issues.

You may contact me at my email address below for some more detailed ideas about how you might best move forward with the Cache-A. Let me know what model and version of software you are running.

Tom Goldberg
TGCS
30201 Rainbow Hill Rd.
Evergreen, CO 80439
mailto:tomgoldberg@gmail.com
https://tomgoldberg.net

[Chuck Johnson]

Tom, you Rock!

Chuck